The present invention relates to the field of magnetic data storage and retrieval systems. In particular, the present invention relates to a thin film structure that exhibits improved thermal dissipation properties and a method of fabricating the same.
In a magnetic data storage and retrieval system, a transducing head generally includes a transducer, a substrate upon which the transducer is built, and an overcoat deposited over the transducer. The transducing head often times further includes a basecoat, which forms an interface layer between the substrate and the transducer, and is generally formed of an insulating material. The transducer, which typically includes a writer portion for storing magnetically-encoded information on a magnetic media and a reader portion for retrieving the magnetically-encoded information from the magnetic media, is formed of multiple patterned layers successively stacked upon the basecoat.
The transducer layers, which include both metallic and insulating layers, exhibit different mechanical and chemical properties than the substrate. The differences in properties affect several aspects of the transducer, including pole-tip recession/protrusion (PTR) of the metallic layers of the transducer relative to the substrate at an air bearing surface (ABS) of the transducing head.
During operation of the magnetic data storage and retrieval system, the ABS of the transducing head is positioned in close proximity to the magnetic media. Performance of the transducer depends primarily upon the head-media spacing (HMS), which is the distance between the transducer and the media. Preferably, the HMS is small enough to allow for writing to and reading from the magnetic media with a large areal density, and is great enough to prevent contact between the magnetic media and the transducing head. However, PTR at the ABS is considered to be a primary technical gap for hitting required HMS targets. During high drive ambient temperatures, PTR decreases HMS, which increases the risk of head-disc contact and the attendant mechanical reliability problems. Alternatively, during a cold write PTR can increase the HMS to the point of degrading writeablity, signal-to-noise ratio, and bit error rate.
The effects of PTR generally result from thermal pole-tip recession/protrusion (TPTR), current-induced recession/protrusion (CPTR), or a combination of TPTR and CPTR. TPTR arises from isothermal (global) temperature changes in the transducing head during drive operation. TPTR is proportional to the difference in coefficients of thermal expansion (CTE) between the transducing head and substrate materials. The CTE of materials used in forming the substrate are typically much smaller than the CTE of materials used in forming the metallic layers of the transducer. As such, when the transducing head is subjected to high operating temperatures, the transducer's metallic layers exhibit greater expansion compared to the substrate. This greater expansion causes the metallic layers to protrude closer to the magnetic disc than the substrate.
CPTR results from localized joule heating during application of currents to the writer coil and the resultant heat dissipation into the surrounding components of the transducing head. CPTR, in contrast to TPTR, is proportional to the first order of the ΔT(CTE) product, where ΔT is the localized temperature rise in the writer core, and CTE is based on the core fill material (i.e., the insulating material generally disposed around the writer coil in the writer core). At large write currents in the writer coil, ΔT can be more than 20° C., causing CPTR to exceed 0.3 micrometers, which is a large fraction of the total fly height budget. In the drive, heat transfer to the disc will reduce this value by 3-5 times, but it will still be a large portion of the total fly height budget. As such, CPTR places constraints on the amount of write current utilizable. Accordingly, there is a need in the industry for preventing significant TPTR and CPTR changes with temperature.